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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASAE. 34(1) 0269-0274. (doi: 10.13031/2013.31657) @1991
Authors:   C V.Schwab, R.A.Curtis, S.A.Thompson, I.J.Ross

ABSTRACT One of the most popular methods of determining potential locations of spoilage in stored grains is through constant monitoring of the internal temperatures of the grain mass. Distinctive increases of the local temperatures in the grain are a good indication of potential spoilage problems. Daily inspection of the internal temperature of the stored grain can detect the presence of a "hot spot" before any grain is seriously deteriorated. The operator can then choose to aerate the grain to cool the "hot spot" or remove the grain from the bin. Daily monitoring of temperatures requires that sensing elements be placed within the grain mass. A common method of monitoring temperatures in a mass of stored grain utilizes thermocouples attached at regular intervals to high-strength steel cables. The entire assembly including the thermocouples and the cables is coated with a protective jacket. Temperature-sensing cables are available in many types, differing in surface material, size and cross-sectional shape. These cables are typically suspended from a grain bin roof in a standard pattern so they form a three-dimensional matrix of temperature monitoring points. Article was submitted for publication in January 1990; reviewed and approved for publication by the Structures and Environment Div. of ASAE in July 1990. Presented as ASAE Paper No. 89-4002. This work is published with the approval of the Director of the Kentucky Agricultural Experiment Station and designated as Paper No. 89-2-113. Major funding for the research reported in this article was provided by the Farm and Industrial Equipment Institute, Chicago, IL, and the University of Kentucky Agricultural Experiment Station. Part of the equipment used in this research was donated by Brock Mfg. Co., Inc., Milford, IN; Butler Mfg. Co., Kansas City, MO; Chief Industries, Inc., Grand Island, NE; Clayton & Lambert Mfg. Co., Buckner, KY; Floss Food Technology Corp., Eden Prairie, MN; and Mix-Mill Mfg. Co., Inc., Bluffton, IN. The authors are C. V. Schwab, Assistant Professor, Agricultural Engineering Dept., Iowa State University, Ames; R. A. Curtis, Research Assistant, Agricultural Engineering Dept., University of Kentucky, Lexington; S. A. Thompson, Associate Professor, Agricultural Engineering Dept., University of Georgia, Athens; and I. J. Ross, Professor and Chairman, Agricultural Engineering Dept, University of Kentucky, Lexington. These cables are subject to vertical frictional loading during filling, storing, and emptying operations. Since these cables are supported by the roof of a grain bin, designers require design guidelines for estimating the magnitudes and characteristics of the vertical loading. The loads imposed on temperature sensing cables have caused localized failures in certain components of grain bins as reported by Wickstrom (1980). The purpose of this study was to compare five different types of commercially available temperature sensing cables to determine the apparent coefficient of friction of wheat on the cables and the magnitude of vertical loading in a full-scale grain bin during both static and dynamic unloading conditions. The effects of emptying flow rate, starting grain height, detention time, and the radial position of the cables in the bin were determined. EXPERIMENTAL METHODS The experiments consisted of two parts: a laboratory study to determine the apparent dynamic coefficient of friction of grain on the cable surfaces; and a full-scale bin study to measure vertical frictional loading on the cables. Five types of temperature cables which represent several of the variations in commercially available cables were used in the experiments. The different dimensions and surfaces materials of the cables are given in Table 1 and the physical appearance is shown in figure 1. The cables used for the laboratory study were short sections identical to the cable specimens used in the bin study. The grain used was soft red winter wheat at 11.9% moisture content (wet basis) with an uncompacted bulk weight of 772.6 kg/m^. The influences of different variables on parameters measured were determined using analysis of variance technique in SAS (1982). The laboratory study was conducted to determine the apparent coefficient of friction of wheat on the temperature cables at different normal pressures. The magnitude of the

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